TT Install with Solar - RCD question

[IAmSparkytus!]

Hello

Need to replace a distribution board in the next few weeks to allow for more circuits to be installed in January.

Existing is a TT system with a solar installation fitted.

Current install has a 100A TP incomer, meter, C63 TP MCB, solar install, 100ma RCD, distribution board fitted with more MCBs than there are RCBOs.

Please see photo attached.

I have no experience with solar installations. Am i “allowed” to relocate the enclosures and shorten the tails going to them?

Can these tails be covered by my new proposed 100A 100mA time delay RCD or is there a reason they haven’t already been by the previous installer - something in the regs relating to this maybe?

Proposing to go from the meter to a 100A 100mA switch, then to solar, then to new DB with 30mA protected circuits throughout.

There’s a few three phase circuits but nothing requiring additional protection (cables supply air conditioning and refrigeration condensing units and not hidden within walls, no sockets etc etc) so going to omit the 30mA protection from these.

Look forward to your input.

Thanks

 

[pc1966]

Proposing to go from the meter to a 100A 100mA switch, then to solar, then to new DB with 30mA protected circuits throughout.

That sounds perfectly sensible.

I would say to check the solar inverter manufacturer's instructions about the type of RCD that is permitted. If it is fine for type A then no problem in finding one for your "100A 100mA switch" (presumably the delay/selective RCD) before the DB.

If they require a type B then cost is going to be much higher and very few make them, Doepke are the only ones I have noticed by no doubt a few like Schneider and ABB do them for a largely EU market.

There’s a few three phase circuits but nothing requiring additional protection (cables supply air conditioning and refrigeration condensing units and not hidden within walls, no sockets etc etc) so going to omit the 30mA protection from these.

Your issue with doing that is no selectivity - if any of them have a L-E or N-E fault then your incomer will almost certainly trip as it is very unlikely your Ra will be low enough to clear on any MCB's magnetic trip (which is faster than a selective RCD).

 

[IAmSparkytus!]

Thanks for the reply. Noted about omitting the 30mA RCDs, will look at purchasing 4pole 30mA RCDs and a larger enclosure to house those and our proposed SPD.

Do you have experience with those solar energy units? Done a bit of Google’ing and can’t find anything on them. There are 3 of them so potentially 1 per phase but they all look to be connected together as well.

Can’t see any cables coming from them heading to solar panels etc, customer says he doesn’t have solar panels.

Another thought is the possibility of them being battery packs rather than some sort of solar setup?

 

[pc1966]

Thanks for the reply. Noted about omitting the 30mA RCDs, will look at purchasing 4pole 30mA RCDs and a larger enclosure to house those and our proposed SPD.

It can be cheaper / simpler to have a DIN box beside the DB for added RCDs than trying to find cost-effective RCBO options for 3P circuits.

Do you have experience with those solar energy units? Done a bit of Google’ing and can’t find anything on them. There are 3 of them so potentially 1 per phase but they all look to be connected together as well.

Can’t see any cables coming from them heading to solar panels etc, customer says he doesn’t have solar panels.

Another thought is the possibility of them being battery packs rather than some sort of solar setup?

I don't see any info in your post or photo, certainly if there are no solar panels it would seem strange! I can't imagine battery packs being of that much use without some for of local generation, beyond your UPS sort of arrangement for keeping computers going.

 

[davesparks]

Can these tails be covered by my new proposed 100A 100mA time delay RCD or is there a reason they haven’t already been by the previous installer - something in the regs relating to this maybe?

Solar should not be on the load side of any RCD which is shared with any normal circuit. Hopefully the reason is obvious, although I guess the issue will be reduced if the RCD is for fault protection only.

 

[davesparks]

Can’t see any cables coming from them heading to solar panels etc, customer says he doesn’t have solar panels.

What makes you think they are solar inverters, wouldn't it be more likely that it's something like one of those 'voltage optimiser' scams?

 

[pc1966]

Solar should not be on the load side of any RCD which is shared with any normal circuit. Hopefully the reason is obvious, although I guess the issue will be reduced if the RCD is for fault protection only.

Good point, I was assuming an up-front RCD is for fault protection within DB, etc, and to cover for a failed RCBO for fault conditions, not as additional protection.